mineral

Glauconite

Glauconite (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2

Hardness: 2.0; Color: Olive-green, dark green, or blue-green; Luster: Dull to pearly; Crystal Structure: Monoclinic (usually micaceous or earthy); Cleavage: Perfect basal (rarely seen in grains); Specific Gravity: 2.4 - 2.95

Hardness: 2
Color: Olive-green, dark green, or blue-green
Luster: Dull to pearly

Identified June 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms in marine environments on continental shelves where sedimentation rates are slow. It is an authigenic mineral, meaning it forms in place from the chemical alteration of existing materials like biotite or fecal pellets. Found primarily in late Precambrian to Cenozoic marine sedimentary rocks.

Uses & applications

Used primarily as a soil conditioner and fertilizer (greensand) due to its potash and iron content. Also used in water softening and as a pigment in green paints.

Geological facts

Glauconite is a key indicator for geologists to identify marine transgression (rising sea levels). It gives 'Greensand' formations their characteristic color.

Field identification & locations

Identify in the field by its distinct dull green color and soft, crumbly texture. It is commonly found in 'Greensand' sedimentary layers in coastal regions like New Jersey, USA, or the south coast of England.

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

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mineral